The present invention relates generally to packet telephony systems, and more particularly, to methods and apparatus for exchanging data, or media, among participants to a conference call.
Communication networks are used to transfer information, such as data, voice, text or video information, among communication devices, such as computer terminals, multimedia workstations, and videophones, connected to the networks. A network typically comprises switching nodes connected to each other, and to communication devices, by various links. Each link is characterized by a bandwidth or link capacity. Information input from the communication devices to the network may be of any form but is often formatted into fixed-length packets or cells.
Packet-switching network architectures are widely used, for example, in popular local-area network (LAN) protocols, such as Ethernet and asynchronous transfer mode (ATM) protocols. In a packet-switched network, data transmissions are typically divided into blocks of data, called packets, for transmission through the network. For a packet to get to its proper destination, the packet must traverse through one or more network switches or nodes. In a packet-switched network, all transmitted information, including data, voice, text and video information, is handled in the same manner by the network.
Packet telephony systems allow the end-point devices in a two-party call to exchange media, such as voice or video information, directly, as long as there is a common compression scheme supported by both end-point devices. In a conference call, however, media connectivity becomes more complicated, where all devices either exchange media pair-wise directly, or using a media mixer. A media mixer, also referred to as a multiple point controller, redistributes media from one connected device to all other listening devices.
The pair-wise exchange of media among conference participants is relatively straightforward, in that it only requires a device to negotiate a media channel with every other device. The pair-wise exchange of media among conference participants, however, exacts a high penalty on network and CPU processing power in each connected device. The exchange of media among conference participants using a media mixer, on the other hand, conserves both network bandwidth and total CPU utilization, and is generally viewed as the preferred solution in commercial grade private branch exchange (PBX) systems.
While the use of a media mixer to exchange media among conference participants conserves both network bandwidth and total CPU utilization for conference calls, conventional packet telephony systems do not permit a mixer to be added to a two-party call when the two-party call becomes a conference call. In addition, a need exists for a packet telephony system that removes a mixer from a conference call when participants drop out of a conference call, leaving only two participants behind, if the remaining parties can exchange media directly.
Generally, a media exchange monitor is disclosed that selectively (i) introduces a mixer into a two-party call when the two-party call becomes a conference call (ad-hoc conference), and (ii) removes the mixer when one or more conference call participants drop out, leaving only two participants behind. According to one aspect of the invention, when a party to a two-party call requests to convert the call into a conference call, by bringing one or more additional parties into the call, the packet telephony system responds to the conference call request by connecting a mixer to service the conference call between the parties. When parties drop out of a conference call, leaving only two parties behind, the mixer is removed from the conference call. In one implementation, the mixer is removed from the conference call only if the two remaining parties can exchange media directly. Thereafter, the two remaining parties are prompted to establish a direct media connection, without participation of the mixer.
According to another aspect of the invention, when the media connection among the parties must be changed to introduce or remove the mixer, the media exchange monitor achieves the desired connectivity by initially querying the parties for their capabilities. Thereafter, the media exchange monitor instructs the parties to establish a direct connection for a two-party call or to connect to the mixer for a conference call. The media exchange monitor processes the results of the capability query to select a compatible compression algorithm.
According to a further aspect of the invention, the encoding scheme is selected to optimize for whether the connection is a two-party connection, or a conference call with at least three participants. Thus, if a two-party call becomes a conference call, a new encoding scheme optimized for conference calls is selected. Likewise, if one or more parties drops out of a conference call leaving only two-parties, a new encoding scheme optimized for point-to-point connections is selected.
A more complete understanding of the present invention, as well as further features and advantages of the present invention, will be obtained by reference to the following detailed description and drawings.